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## [moved] Cadence Virtuoso stability analysis

Does anyone know where I can find a tutorial about how to use the stb (stability analysis) function in cadence? open loop gain close loop phase margin and how to measure the offset?,

When running stb analysis, I would like to see the bode response not just for the entire loop but for some intermediate nodes to figure out how much gain/phase each stage in the loop is giving me. I have not been able to find how to do this in cadence ADE.

## Interpretiing data from Cadence stability analysis

I had enough trouble from the stb analysis (coming up with absurd operating points and giving way-bogus loop gain) that I gave up on it and went back to old school methods. You just can't trust it to work each and every time, like you need to ever get through your Monte Carlo compliance analysis.

## stabilt of beta reference

i have designed a low power beta multiplier refernce (70nA) as shown. The opamp is a 5T diff check for stabilit i broke the -ve feedback loop and plugged iprobe from analoglib in cadence. stb analysis shows phase margin of 20 deg and gain margin of 14dB with C=2pf. I m not able to achive better phase margin even after shifting the mirror po

## DC Gain Measurement using STB in Cadence

Does anyone know of a way of extracting more information from an stb analysis in Spectre than appears on the Direct Plot menu? I need to measure DC (ie low frequency) gain, 3dB point and the phase at an exact frequency. Clearly I can do this using cursors, but that's not a great tool for Monte-Carlo, worst case or parametric sweep simulations. I've

## [CADENCE] STB simulation gives diffrent phase margin than AC simulation

I'm pretty sure at this point that results from AC analysis are correct, while those from stb are not. I've run time analysis with phase margin from AC near 45 deg and at that point circuit starts to generate. Why do you think that ac is correct? The LC method you have applied does not mirror the actual load. Thus, I don't know if this matt

## how to measure parameters of a operational transconductance amplifier(OTA) design

1）~3） AC simulation or stb analysis 4) DC sweep 5) transient 6) DC sweep 7) noise analysis

## Capacitive feedback OTA Design Issues in Loop gain

HI I have designed a capacitive feedback OTA ( OTA is folded cascode single stage OTA with ideal CMFB). When I simulate the loop gain of OTA (using iprobe and stb analysis in cadence) I get a 'High Pass' response at low frequencies. I am not sure why this is happening. Please help to solve this issue. Thanks

## stb analysis for differential amplifier

Hi, I would like to know how to do cadence stb analysis for a differential opamp in feedback(2 path feedback), how should I go about this? Thank you!:grin:

## Middlebrook/Wiedmann in Cadence parameter sweeps Openloop

Like I write on my webpage , Tian's method (as I prefer to call it) is directly implemented in cadence's Spectre simulator as stability analysis (stb), so there is no need to use the complicated formula. Regards, Frank

## The importance of loop gain

Yes you can still use loopgain simulation methodology in cadence. However before running "stb" analysis you have to run transients till your CM is settled. An easier way is to use ideal CMFB circuit and then do can skip the transient analysis part. My answer assumes you already have good background simulation experience in spectre. Let me know if

## How to perform Stability analysis in Cadence

put an iprobe in series at the point where you want the loop to be broken and then do the stb analysis.

## how to do stb analysis in cadence?

type spectre -h stb in terminal for the help file.

## stability analysis for led driver

Hi Include voltage source in feedback net. Star cadence stb analysis. Regards

## Stability analysis for multiple fedback loops

Does anybody have experience how to do stability analysis if more feedback loops are in the circuit? (using cadence ade, spectre) does it possible with the aid of the stb analysis?

## how to use cmdmprobe in stb analysis (cadence)

hi, there. i want to analysis the stability of this full differential OTA(shown below), can anyone here tell me how to add the cmdmprobe in analogLib into this circuit to do the stb analysis? Thanks.

## plot gain and phase margin in cadence

In cadence, you can use stb analysis to do AC simulation.

## Question about LDO ac simulation?

hello, for the AC sim of LDO, you can use RC technique described in philip allen's book (cmos analog circuit design) or iprobe with stb analysis in cadence spectre. both simulations will find open loop gain and phase margin of your LDO. make sure that pass device in LDO always operates in saturation region. hope this helps.

## when design Bandgap, what kind of simulation should be done?

what does ".stb analysis " means?:?: cadence's spectre stability analysis